Manufacture of silicon tetrachloride and carbon disulphide



2,425,504 MANUFACTURE 0F SILIUON'TETRCHLORIDE CARBON DISULP'HIDE Aug.`l2, 1947. A. BELcHETz Filed nec. 29, 1945 Patented Aug. 12, 1947MANUFACTURE OF SILICON TETRACHLO- RIDE AND CARBON DISULPHIDE ArnoldBelchetz, Larchmont, N. Y., assignor to Stauer Chemical Company, acorporation of California Application December 29, 1945, Serial No.637,884

8 Claims. (Cl. 23-205) The present invention relates generally to themanufacture of silicon tetrachloride, carbon bisulde and car-bontetrachloride. It is particularly concerned with a method for thesimultaneous production of silicon tetrachloride and carbontetrachloride in a continuous, unitary process, involving the formationof carbon bisulphide at an intermediate stage.

One of the commonest methods of preparing carbon tetrachloride is by thechlorination of carbon bisulphide, the reactions being essentially asfollows:

The net reaction is thus: 3) 3Cs2+6c123oc14+6s Reaction (1) proceedsquite readily and efficiently, but reaction (2) has proven a source ofconsiderable difliculty in that when sulphur monochloride is reactedWith a large excess of carbon bisulphide, even in the presence of acatalyst, appreciable amounts of the sulphur monochloride still existand tend to remain with the ley-product sulphur. The latter must beutilized to full advantage as a by-product to make the processcommercially feasible as a whole, yet the presence of small amounts ofsulphur monochloride in the recovered sulphur greatly reduces its valuefor most purposes. Hence, it is necessary to employ air-blowing,steaming, and similar operations to make the by-product sulphursaleable, and these operations are expensive and troublesome. It is notfeasible to dispose of the sulphur monochloride from the first reactionas such, as the quantities produced exceed the commercial demand and thesulphur monochloride obtained is not completely pure. The chlorineremaining in the sulphur monochloride must obviously be converted tocarbon tetrachloride, if carbon tetrachloride is to be producedcheaplyhence the necessity for an operation corresponding to the secondreaction.

In addition to the above described difficulties in making carbontetrachloride from carbon bisulphide, the manufacture of the startingmaterial, carbon bisulphide, is also beset with serious problems. Carbonbisulphide is usually made directly from reactive forms of carbon andsulphur, the carbon being brought into contact with sulphur vapor at atemperature of about 13U0 F. or higher. To obtain practical rates ofreaction in commercial operation, it is customary to utilize reactiontemperatures of about 1500 F. Owing to the very large amount of heatrequired to superheat sulphur vapor to this temperature and thedifficulty of doing this in a pipe coil or other eiiicientheat-exchanging apparatus, owing to the extremely corrosive propertiesof sulphur Vapor at high temperatures, the manufacture of carbonbisulphide has heretofore been accomplished chiefly iby what isessentially a batch-Wise operation in cast iron or carborundum retortsor similar apparatus of low thermal eiiiciency. The relatively high costof manufacture of carbon bisulphide adds to the cost of producing carbontetrachloride.

Silicon tetrachloride is a material for which there is a growing demand,and silicon tetrachloride manufacture from metallic silicon,ferrosilicon, or silicon carbide (carborundum) has been hampered by atechnical difficulty substantially the opposite of that encountered inthe carbon bisulphide manufacturing process; namely, that very largeamounts of heat are produced during the reaction, and that onlyrefractory lined Vessels, poorly adapted to the dissipation of heat,have been found capable of withstanding the corrosion. Atypical reactionfor the formation of silicon tetrachloride is as follows:

(4) Si-l-2C12-S1C14 in which silicon in the form of ferroslicon ormetallic silicon is chlorinated with the liberation of a large amount ofheat.

One of the important features of my invention takes advantage of thefact that silicon apparently has a much greater aiinity for chlorinethan have either carbon or sulphur, and that the aflinity of silicon forchlorine is greater than its affinity for sulphur. I have discoveredthat if there is present in a reaction zone at one time a quantity ofsilicon, accompanied by just sufficient chlorine to convert all thesilicon present into silicon tetrachloride; and if there are alsopresent amounts of carbon and sulphur in the proper proportion for theformation of carbon bisulphide, then the simultaneous formation ofsilicon tetrachloride and carbon bisulphide can be achieved at asuitable reaction temperature. Contrary to what might be expected, thereis negligible formation of silicon sulfide or disulphide or of sulphurchloride. However, this result will not ensue if there is present anyexcess of silicon above that required to combine with the chlorine, orif there is excess chlorine. If there is present an excess of silicon,the sulphur will preferentially react with this excess silicon ratherthan with the carbon, so

icon is present, sulphur will react with this ex; cess chlorine to formsulphur rn'onochloride'in'-l stead of reacting with carbon tolformcarbon y The sulphur 'and chlorine krequire-l bisulphide. ments for areaction system Vof the character just described may be quite readilysatised ,en`

tirely or in part by the introduction of sulphur monochloride, such asis obtained as an intermediate or icy-product in the chlorination ofcarbon-bisulphide to form carbon tetrachloride. Silicon and carbonselectively Atake the chlorine and sulphur from the sulphur monochlorideso that .this material can be utilized in the process and, Vdoes notVprovide anir special problem as heretofore. Y A ,Y Y

A, further important feature of the invention is Ytherefore thernethod Ihave discovered of maintaining the necessary stoichiometricproportionalityY between Ythe lsilicon and chlorine present in thereaction Zoneand of maintaining the reactionzone at a suitabletemperature Without use of extraneous heat. This `method involvessubdividing theVV siliconV source material and the carbon sourcematerial (which may, if. desired, be provided byfonematerial, as Vsil-licon carbide). and suspending` them in the re-y actor" Jbyi means`of1the introduced requisite qi'iantitiesV ofv chlorine and sulphurvapor.Y The finelyi divided feed material is continuously inftrod'ucedinto the reactor as a fio-wing suspenf sion in'oneor both 'ofthe gaseousreactants, at a moderate' non-'reacting temperature, andboth thersolid'and gaseous reactants are substantially instantaneously'heated to'Y areacting temperature by c'onvection'an'd conduction from a mass ofiiuidized material alreadypresent in the reaction zone. Thereafter, 'theheat required to continue the process,` asv additional quantities 'ofreactantsar'e introduced, is supplied bythe heat evolved in theformation of silicon tetr'achloride from the silicon and chlorine.

The 'amount of heat heeded to balance the requirements of the -processwill depend upon the relative amounts of silic'ontetrachloride andcarbon bisulphide produced.Y .By/allowing therh to be formed in the4reactor inthe proper ratio, a substantially exact balance can be reachedsuch that 'heat need not vbe supplied to the reactor fron an extraneous'sourcej i, e., the lreaction 'can' be n'iade adiabatic. Thisheatebalanc'- ing feature is an Vespecially important element of i'nyinvention forV it enables the carbon bisulphide to be produced vvithoutany difficult heat input problem and silicon tetrachloride to beproduced under Vsuch conditioi'isth'at the rel'- atively 'greateiiotherinicitv of the raction does not presentaproblem. f e Y i At thepreferred operation temperature 'of about 1520 -forthe conjoint Yandsimultaneous formation of silicon tetrachloride and tion f H 5) Y issuchthat only about 91% of the' sulphur incarbon -bisulphide, theequilibrium fior the reacreactor.

troduced into the reactor isconverted to carbon bisulphide in thepresence of excess carbon. The unreacted sulphur, silicon tetrachlorideand carbon bisulphide leaving the reactor as reaction products arereadily separated, e. g., by fractionation. Thereafter, allor a portionof the carbon disulphide may' be chlorinated'to carbon tetrachloridewith simultaneous Yformation of sulphur monochloride. This is separatedfrom the carbon tetrachloride and is returned to the bon bisulphidebeing chlorinated, the sulphur monochloridercan provide all or part ofthe sul- Y phur required for production of carbon bisul- Y a batchleactiand avIniXtiire Ovfchloi'ine and sulphur vapor passed therethrough,the'silicon inass in the furnace Will be in 'great excess over thechlorine quantity pre'sentr'at any-given instant so that silicondisulphide Will be formed invaddition to silicontetrachloridayvithalittle, if any, forinati'cn Yf carbon bisulphidefWhen the silicon is exhausted Airoir the bed, ala'rge quantity ofunreacted carbon will remain, with no heat available to convert thecarbon to carbon bisulphide. -f

The principal object of rny. invention is to ,sur-4 mount theaforementioned,difficulties, to provide an economical, continuousandeasily-managed unitary process for vthe "simultaneous manufacturegcfV4silicon tetrachloride and carbon bisulphide and, if desired, theconversion of all or part of the latter into carbonwtetrachloride.

More specifically, one of the, important objectsr of Vthe invention isto afford amethod for the conjoint forniationi Ofzsilicon tetrachlorideand carbon bisulphide; in which the exothermic heat of `the 'former andthenecessary preheating of the sulphur'4 for Athe latterare-'mademutually advantageous, each vservingto remedy the diincultiesoccasionedy bythe other. v Y, A further -objelct of myginvention is Vtoprovide a process for manufacturing silicon tetrachloride and carbontetrachloride from silicon, carbon and c-'nlorinie wherein the.heatrequired to betrans- Yferred from fand to the reactants aresubstantially g lessfthan inV prior known processes, and wherein sulphur-andhalogena'tedsulphur icy-products re'- sulting ,from the intermediateformation and chlorination of carbon bisulplfiideare continuous= Y lyreturned 'to the process.v

Still another l*object of uthevinvention is to'provide an effectiveVrneth'od -of continuously produc;- ing silicon tetrachloridesiniulta'neously` in a come rnon reaction zone. Theinvention hasotherob.; jects and produces other. results iof advantage `v'vhich, togethervvith' the .'forego'ing, will more inventio'nher'einaf-ter given. Y Y

In the 'drawing'gaccompanying-and forming va part hereof, the' singlegure isa `diagraifnrr'iatic representation 'of suitableifapparatuswhich. can

Vfully appear 'from the :detailed descr-iptionof `the lv.beemployedyanda flow sheet: Referring nowfto the drawingf'andby; Wayof`explariation of Y suite @ble equipment Whhcan. 'bei ,employed Q @anyyout lthe vprocess or. my invention, vessel ,Q -is' an elongated,vertically extending reactor, pre'fer- Y Depending upon the quantity ofcar- Y 'ably lined with refractory in which the joint formation ofsilicon tetrachloride and'earbon bisulphide is to take place. Thematerials to be reacted are fed into the reactor through line I2. Thesolids are preferably placed in hopper 6 as a uniform mixture, and arewithdrawn from this by the screw pump on feeder I driven by motor 8. Thesolid reactant materials emerging from the solids pump I into line IIare picked up in gaseous suspension by a stream of sulphur monochloridevapors entering through line 86, the latter being vderived from asubsequent step of the process. In starting up the process before anysulphur monochloride has been produced, chlorine may be introduced intoline 86 through line I and used to suspend the solids. The suspendedmaterials next enter line I2 where they join a stream of sulphur vaporsbeing generated in a vaporizer I4.

In order to establish suitable operating conditions in the reactor 9 andto place the process in operation, a quantity of carbon is initiallyintroduced into reactor 9. This initial charge is heated to or above thechosen reaction temperature by passing hot flue gas, or any other heatedinert gas which may be available, through line I2 into reactor 9, thenceinto line 22 and releasing it through line 35. A combustion chamber I Ifor generating a suitable hot inert flue gas is connected by line I8 toline I2 to supply products of combustion for raising the temperature ofthe reactor. Air is supplied to the chamber by line I9 and fuel by line2 I. The passage of the heated inert gas is continued until the reactorand the material in the reactor has reached an elevated temperature. Thepurpose of this initial step is to establish inthe reactor a bed ofheat-storing material capable of transferring heat by convection andconduction to gaseous and solid reactant materials subsequentlyintroduced. Since the function of the initial charge of material ispurely a physical one, it would be feasible to employ any inertsubstance, but as previously mentioned, I prefer to use a material whichis to be employed in carrying out the reaction, such as carbon. Y

When a suitable elevated temperature has been established in thereactor, the flow of heated flue gas through line I8 is interrupted andthe solid reactants, consisting of metallic silicon, ferrosilicon orsilicon carbide and carbon from hopper 6, are picked up by the screwpump on feeder 'I and discharged into line II. Any combination of theabove-mentioned ingredients may be employed which will provide thenecessary amounts of silicon and carbon for the formation of the desiredamounts of silicon tetrachloride and carbon bisulphide in the properratio. Preferably, however, I employ ferrosilicon and a form of carbonwhich is reactive with sulphur, such as wood charcoal which has beenheated previ- .ously to remove hydrogen and oxygen. The materials arepreferably in the form of particles not larger than about 50 mesh; Ihave found that a particle size between 100 and 200 mesh is particularlysuitable.

The combined stream of material in proper proportions for the formationof silicon tetrachloride and carbon bisulphide, with no excess siliconor chlorine present, is, until its entrance into reactor 9, at atemperature too low for the commencement of the desired reactions. Uponentering the reactor 9, however, and being intimately and rapidly mixedwith the preheated bed of heat-storing material, earlier described,

th'e gaseous and solid reactants' are almost in stantaneously heated toat least a temperature Whereat the reaction of silicon with chlorinecommences. As this reaction continues, it evolves heatsuicient inquantity to superheat the sulphur vapors toa temperature such that theycan react with the carbon which is also present to form carbonbisulphide.

' The 'superheating of th'e sulphur vapors deserves special mention, asthis is not simply a matter of sensible heat. At the boiling point,sulphur vapor is composed of sulphur molecules which are a mixture of Seand Ss, but when heated to the reaction temperature of approximately1520 F., the sulphur dissociates to S4 and finally to S2 molecules. Thedissociation of sulphur vapor from Seto S2 is highly endothermic. Oncethe reaction between sulphur and carbon commences, a moderate quantityof heat of lreaction is liberated, but this effect is entirelyovershadowed by the much greater heat absorption in the dissociation ofthe sulphur from Ss to Se.

In passing through the reactor 9, the silicon and chlorine reactsubstantially quantitatively to form silicon tetrachloride, while thesulphur introduced reacts to the extent of about 91% to form carbonbisulphide. The carbon is introduced in the stoichiometric proportionrequired by the quantity of sulphur which is converted to carbonbisulphide. The reactor vapors pass into the condenser 23 and thecondensate and any uncondensed gases flow through line 24 into areceiver 26. The uncondensed gases pass through line 2'I into arefrigerated condenser 28, wherein further liquid products are obtainedand collected in the receiver 3|, while the uncondensed portion isreleased through line 32. Liquid collected in receiver 3| is returned toseparator 26 through line 30. The liquid collected in the separator 26will include any unreacted solids such as carbon which may escape fromthe reactor and any ferric chloride and other impurities which aresolids at the temperature of condensation of the principal products. Thepresence of ferric chloride may arise from the use of ferro silicon asthe silicon source material. The liquid in separator 26 will consist ofa mixture of silicon tetrachloride and carbon bisulphide with elementarysulphur dissolved therein.

The materials collected in receiver 26 are removed through line 25 andforced by pump 20 into line I5 and thence through filter I3 wherein theabove-mentioned solids are taken out. The claried liquid phase is thenpassed through line I0 into a vaporizer 33 in which, by carefullycontrolled heating, the volatile products are revaporized, leavingliquid sulphur to accumulate in the base of the vessel free of anysubstantial quantity of silicon tetrachloride or carbon bisulphide. Heatfor the vaporization is supplied by heating coil 34 positioned in thebottom of the vaporizer. 'Ihe liquid sulphur collected in the bottom ofthe vaporizer 33 is discharged through line 36 by pump 31 to the moltensulphur tank 38.

It will be appreciated that the sulphur withdrawn through line 36constitutes that excess which is necessary to charge to reactor 9 toproduce the desired amount of carbon bisulphide and that this quantityof sulphur can be continuously recycled through the process. The freshsulphur feed is supplied through line 39 to tank 38. The total moltensulphur feed flows through line 4IA to pump 42A and is charged throughline I6 into the sulphur vaporizer I4.

The mixed vapors of silicon tetrachlorideand carbon .bisulphide pass offtfrom vaporizer 33 lthroughline 4l and are 'partially or whollycon---densedlin condenser f 42 Whencethey flow through line-ll3 into .themid-section of iractionatin-g-col- -umnll'lL which is 4,provided With are-'boiler 16v-in the base thereof. Silicon Y tetrachloridefisremoved:fromthe base ofthe column through' line Y4l into portion is removedfrom the'system through liner t2. Carbon bisulde `from;.pump.59is alsopassed 'through'line .63 and 'is admitted t0 "a chlorinator 64 intowhich chlorine isadmit-ted through -line `66. A Avapor' -line -6'1 .isprovided at the top of the :chlorinator B4 and is connected to :acondenserV 68, from which condensate flows through li-ne 619 -back tothe chlorinator 64.

The chlorination of car-bon bisulde to carbon `'tetrachloride ,fandsulphur monochloride is conducted at-atmospheric pressure and the heatof reaction is absorbed bythe vaporiZat-ion of carbon tetrachloride..The amount or" liquid in the ychlorinator -is large relative toquantity Toi carbon Vbisulphide introduced-and vsin-ce the ch1orinationreaction takes yplace very rapidly, itfis .possible b y proper draw,vtliroughline 65, a-'stream of liquid fmate'- -rial gwhich issubstantially entirely composediof carbon tetrachloride and 1sulphurmonochlor-ide vand Which ;contains ronly 'a negligible amount ofAunreacted carbon bisulphide. The :produ-ctsirom .the chlorinator -pasrsthrough line 65 into pump T0 land -are transferred Avthrough line 'l5into a f-ractionating column 80. Carbon .tetrachloride lis distilledoverhead through -line .1l into a conl denser 1.2, the liquied .carbontetrachloride being transferred through line .Teinte a-receiver 14,1Avwhence itis Aremoved through `-line 16 .and ,transferred by pump L1partly vintogline;18 -as reflux to column Bil-and partly for 'removalasa -product through Eline 1.9. are-boiler -81 yat the ibase for supplyingthe heat `required Ain con-ducting the fractionation.

v .The sulphur chloride-collecting .at the -base of 'thercolumn -isremoved through linepfZ 'into a .pump `@8.3 which vchanges =the sulphurvfchloride f i .through .-line 1.8.4 to .a'sulphur chloride vapori-zer8.5; .sulphurmonochloridevapors from 85 epass through AlinelSS to thedischarge'oi screvvpump .11, :and-convey-the solid reactants vasfasuspension ,through .line =Ii -into line t2 Yand thence to relactor. Y K*Y A y In the event-that fall -or nearly Yall theycarbon -bisulphideisfldisposed'cf .-as such fthroughpline B2, so that konly silicontetrachlorideand carbon bisulphideeprovide the end products, gcl'ilorineis Yintroduced into the vscrew .pump from line L0 Ainstead of sulphur:monochloride through lineg's. .Referring now more ,particularly `to-.theselection Vof :.propervoperating f conditions for `the prac- 'ticerofthefinvention, `considerable'flatitude Ais vpermissible, V.dependinguponr'fthe rays/materials fused-andupon thematic in .which silicontetrachloride, carbon AIbisulphide andA carbon vtetrachloride are to bemanufacturedfasfend prodj ucts.` Ordinarily, *I* prefer to adustgthevariables control of the feed to with- Column 80 includes vto Yachieve,adiabatic operation ofthe reactor 9. This adustment will Vobviouslybeaffected by the reaction temperature and the amount -of preheatsuppliedV in vvaporizer |4, Vvaporizer 85, and the temperature of theincoming solids.

lIn a typical case, Where the `outlet vapors from Ysulphur vaporizer lllvvereat 850F., the sulphur monochloride vapors from vaporizer 857Were at285 F., and the solids 'were introduced 'at 100 F., the adiabaticoperation required that about 1.4 lbs. of carbon bisulphide be producedper pound of Asilicon tetrachloride, the reactor tem- 'peraturebeing-about 1520o F. The above Weights of products will be accompaniedby about 0.1 lb.V

of unreacted sulphur delivered from line 36. The quantity of sulphurmonochloride which must be supplied to the reactor to furnish chlorineto Y form each vpound of silicon tetrachloride is about 1.6 lbs., andthis amount Willvbe produced .byv

the chlorination .of only `0.9 lb. of carbon bi- Ysulphide. Hence, ofthe total of 1.4 lbs. of-carbon bisulphide produced per pound of siliconvtetrachloride, 0.5 1b.v will be available for `disposal as such, `orifdesired, for chlorination to carbon tetrachloride in a .separateoperation'. If all 1.4 lbs. of carbon bisulphide are converted to carbontetrachloride, there will be 2.8 lbs. of the latter per pound of-silicontetrachloride. If only 0.9'lb. of carbon bisulphide are converted,'therewill vbe 1.8 lbs. of carbon tetrachloride :per .pound of silicontetrachloride.

With different Ytemperature conditions ymaintained Yin the retort .andlin the sulphur .vaporizer and sulphur monochloride Vaporizer, ofcourse, it will `be necessary toproduce dilerent weight ratios ofsilicon `tetrachloride .and carbon bisulphide for adiabatic operation.In the event that higher proportions of carbon bisulphide -and/or carbontetrachloride are desired per pound :of silicon tetrachloride, Vthen thereactants should be Vheated. to vhigh temperatures, orY conversely, ifya higher ratio .of silicon tetrachloride .is V de,- sired, then thereactants shouldlbe at lower teinperature when 'they enter the reactor.This merely `follows from the fact that silicon tetrachloride formationis the heat producer, [While carbonbisulphide vformation `is .theYheatzfconk Y sumerL Ifit `is `desired V-to increase the extent of.silicon tetrachloride formation, liquid .silicon ftetjrachloride -can-be .introduced directly into the .re-

production vof carbon Vbisuliide .as the ,heatgconsumer. IfA it isldesired to maintain .the silicon Ytetrachloride production atarelativel-yhigh level andyet not increase the carbon loisulde-produc.-

tio-n toogreatly, heat can be taken 1up' byfintroducing .a Apart .ofvthe vsulphur :monochloride vfrom line 84 through line 93,.,i-n'liquidiorm, orpartrof the requisite ramountof .sulphur,canbe-passedin liquid ...phase directly from line .i5 ythrough `.line9.4

.and ,line `92t`o the reactor insteadofthroughlines `l and l2. n Y

` Assuming that thesolidffeedmaterialsare reduced toparticle sizesbetween 100.and2 00 mesh,

thesupercial vapor velocity through the .reactor Vshould `be between:about .1 and 3 '.feetgperfsecold, toachieve-,a suitableextentofsuspension therein. TheheatY-storing bed. .of .carbon originallyLi'ntro- .duced is maintained .by always introducin'glsulphur vandgc'arbon .in their combining ratios, and carbon is neither added .to norremoved {fr-'om the :f mass Y of the Vorigir1a`.1- heat-storing Vcarboncharge.

To `illustrate practice ofthe invention, metallic silicon and carbonWereplaced in hopper 6 in a proportion of 28 pounds ofV silicon to 48pounds of carbon. v'Ihis mixture was fed by screw pump 1 into line `Ilat the rate of 76 pounds per hour, 142 pounds of chlorine gas beingintroduced through lineV I0. Sulphur, vaporized in the vaporizer IG, wassupplied through line I2 at the rate of 284 pounds per hour. Reactor 9had previously been heated to` a temperature of about 825 C. The mixtureof metallic silicon, carbon and chlorine Passed into the reactor whereinthe silicon was converted to silicon tetrachloride and the carbontocarbon disulphide. A slight excess of carbon was employedjinitially soas to establish a light carbon -bed in the reactor. The rate ofintroduction of the materials was so regulated that the Vapor velocityin the reactor Was at the average rate Vof 1.5 feet per second with anaverage theoretical retention time in the reactor of seconds. Thereactor was operated at 5 pounds gauge. I

The reaction products passing out through line 22 included silicontetrachloride, 168 pounds, carbon bisulphide, 304 pounds, and 28 poundsof unreacted sulphur. These materials Were passed into -the condenserI23 and then into receiver 28. The excess sulphur present was finallyrecovered through line 36A from partial condenser 33. The silicontetrachloride was recovered through line 52 while the carbon bisulphidewas taken off through line 62.

To illustrate practice of the invention Wherein carbon tetrachloridecomprises one of the principal products, and sulphur and chlorine aresupplied by the .sulphur monochloride, a mixture in the proportion of 28pounds of silicon to 38 pounds of carbon was fed into hopper 6. 'I'hismaterial was then discharged from screw pump 'l at the rate of 76 poundsper hour. However, 270 pounds of sulphur chloride were vaporized in sulnphur monochloride vaporizer 85 and Were supplied through line 86 attemperature of 140 C. In addition, 93 pounds of sulphur were suppliedfrom a sulphur vaporizer through line I2 While no chlorine was suppliedfrom line l0. These reactants, upon introduction into the reactor 9,produced 170 pounds of silicon tetrachloride, 239 pounds of carbonbisulphide, and pounds of unreacted sulphur, the latter being recoveredfrom the line 36 and added to the molten sulphur in the sulphur meltingpot 38. The silicon tetrachloride was recovered from the first refluxcolumn 44 through line 52 and comprised 170 pounds. The carbonbisulphide available from receiver 5l was drawn off at the rate of 87pounds of carbon bisulphide per hour While 152 pounds per hour werediverted through line 63 into the chlorinator 64 into which chlorine wasintroduced at the rate of 426 pounds per hour. 308 pounds of carbontetrachloride and 270 pounds of su1- phur chloride were transferred tothe second rectifying column 69 to give as a nal product 308 pounds ofcarbon tetrachloride and 270 pounds of the sulphur monochloride whichwas returned through line 84 to the sulphur chloride vaporizer.

In place of diverting part of the carbon bisulphide as a product, allthe carbon bisulphide can be chlorinated. However, in this instance,excess sulphur monochloride will be produced and it will be necessary totake off this from the operation instead of carbon bisulphide.

In place of using metallic silicon, one can use other silicon sourcessuch as errosilicon or silicon 10 carbide. In case other silicon sourcesare utilized, attention must be given to the other constituent orconstituents necessarily present. Also, While I have mentioned the useof chlorine, and have indicated thatthe mixture added to hopper 6comprised; siliconand carbon, silicon has the ability to react with`chlorine selectively and chlorinated hydrocarbons can therefore beemployed. Thus, one can successfully use carbon tetrachloride,perchlorethylene or other chlorinated hydrocarbon (preferably oneconsisting of only carbon and chlorine) to supply a portion of thecarbon and all ofthe chlorinel required in the operation.

I claim: g 1 n 1. A process for manufacture of silicon tetrachloride andcarbon bisulphate comprising forming a gaseous suspension of a solidmaterial including available silicon, available sulphur, availablecarbon and available chlorine, the suspensioncontaining silicon,sulphur, carbon and chlorine substantially in the proportions requiredfor the reaction introducing said suspension into a reaction zonewherein the silicon is chlorinated to SiCl4 and the carbon issulphurized to CS2, removing the gaseousv products ,of reaction from thereaction zone and cooling theV same to liquefy the SiCl4 and CS2,and'separating the SiClf:= and CS2.

2. A process for manufacture of silicon tetrachloride and carbonbisulphide comprising forming a gaseous suspension of a solid materialincluding available silicon, available sulphur, available carbon andavailable chlorine, the suspension containing silicon, sulphur, carbonand chlorine substantially in the proportions required for the reactionintroducing said suspension into a reaction zone wherein the silicon ischlorinated to SiCl4 and the carbon is sulphurized to CS2, removing thegaseous products of reaction from the reaction Zone and cooling the sameto liquefy the SiCli= and CS2, separating the SiCh and CS2, chlorinatingat least a portion of the CS2 to form C014 and S2012, and returning atleast a portion of the S2Cl2 to the reaction Zone as a source of sulphurand chlorine.

8. A continuous process for formation of SiCl4 comprising forming agaseous suspension in a reaction zone of silicon, chlorine, carbon andsulphur, maintaining in said reaction zone a temperature conducive toformation of SiCl4 and CS2, the proportion of silicon, chlorine andsulphur introduced and present in said zone for reaction being at leastthat substantially required for reaction maintaining said, suspension insaid Zone for a period suiiicient to ensure substantial completion ofthe reaction, and recovering the SiCl4 and the CS2.

4. A continuous process for formation of SiCl4 comprising forming agaseous suspension in a reaction zone of silicon, chlorine, carbon andsulphur, maintaining in said reaction zone a temperature conducive toformation of SlCh and CS2, the proportion of silicon, chlorine andsulphur introduced and present in said zone for reaction maintaining;said suspension. in. said zone forl a period sucient. toY ensure;substantial completion of the reaction, recovering and;Y separating the.SiCl4 and the CS2, reactingat'leasta portion of the separated CS2 withchlorineta form: carbon tetrachloride and a sulphur chloride',separating the sulphur chloridek and returning tothe reacttion zone atleastfa portion of the sulphur'. chloride asa source of sulphur and ofchlorine..

5. A continuous process for formation ofv SiCh and CS2 comprisingsimultaneously' (a) chlorinati'ngf silicon to form. SiC14` andi (b)sulphidizing carbon toiform CS2 in acommon reaction zone, removingproducts of' reaction from saidzone and recovering the SiClt` and the.-CS2,- they quantity of SiCli.l formed in said reaction zone being:`sufficient to: maintain saidv Zone at a temperature-Y conducive toformation of CS2 without external heating of said zone. t

6. A continuous processfcr formation of SiC14 and CS2 comprisingsimultaneously (a) chlorinating silicon to form; SiCli and (b)sulphidizing carbon to form, CS2l in'V as common reaction Zone, removingproducts of reaction from said`zone and recovering the S1014and'therCS'2, the. quantityy of SiCl4 formed insai'd reaction zone beingYsufficient to maintain-said' zone ata temperature-,conducive tokformation ofi CS2..- without. external heating of saidzone.,chlornatin'g" at. least a portionv of the CS2 to CCli andS2C12, andreturning' at Ieastfsome of the S2C12'to. said zone asV a. sourceOf'sul'phur and of chlorine;

7; A continuous process for formation of' SiCli Y and CS2: comprisingsimultaneously (Sa)` chlorinating silicon to form; SiCLr. and (b)sulphidizin'g carbon to'- form CS2 in a Vcomm-on reaction'zone,removingV products of reaction. from: said: zone and recovering theASiC14 and:v the-CS2', the quantities of SiCl'i` and; of' CS2` formedjinv saidv zone each being suchV that; said Zone:l is. maintainedundersubstantially adiabaticconditionsand at a temperature conducive toformation offSiCliand CS2.

8'. A continuousv process for formation of SiCl-i and'- CS2 comprisingsimultaneously (a) chlorinating silicon to formV SiCli and' (`b)`-sulphdizin'g carbon to f'orrn CS2 in acommon reactionlzone, removingproducts of reaction from saidV zone and recovering the SiCli. andi theCS2, the quantityy of CS2 formed' in.r said zone being sui'cient to takeup-heatiV liberated;v upon formation oi said SiCllr. and to maintain thereaction. zoney at' a temperaturev conducive to formation: of both `CS2and SiCl4.

ARNOLD BELGE-EEZ.

